A soil conditioner and its preparation method and method for improving soil quality

Abstract

The present invention provides a soil conditioner and a method for preparing the same and improving soil quality, and relates to the technical field of soil conditioning. The soil conditioner is prepared from the following raw materials in parts by weight: 35-45 parts of sludge biomass charcoal loaded with calcium chloride; 5-10 parts of corn cob plant extract; 5-15 parts of polyferric silicate sulfate; 5-10 parts of nano zinc oxide; 10-20 parts of phosphate minerals; and 3-5 parts of sodium polyacrylate. The plant extract and nano zinc oxide are first mixed and reacted in a mass ratio of 1:1 to obtain coated nano zinc oxide, and then the soil conditioner is obtained by mixing and granulating with other raw material components in the parts by weight and drying. The soil conditioner of the present invention has multiple functions such as adjusting soil pH, increasing soil organic matter content, reducing the content of heavy metal cadmium, arsenic and other pollutants in the soil, and increasing crop yield, and the dosage per mu is less than 100 kg, without secondary pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioning, and in particular to a soil conditioner and a method for preparing the same and improving soil quality. Background Art

[0002] The quality of soil environment directly affects the safety of agricultural products. In recent years, the soil environment has faced multiple problems such as soil acidification, decreased fertility, and heavy metal pollution. These problems not only affect agricultural production, but also pose a threat to the ecological environment and food safety. Through soil conditioning, we can eliminate or prevent adverse factors that affect crop growth and cause soil degradation, improve soil properties, increase soil fertility, and create good soil environment conditions for crops, making them more suitable for plant growth.

[0003] At present, experts and scholars at home and abroad have carried out relevant research work on soil conditioning issues and formed a series of technical products. For example, the existing Chinese patent document CN 113667482 A discloses a carbon-based composite material. The scheme repairs the soil contaminated by heavy metal cadmium and arsenic by mixing modified biomass charcoal, ironmaking water-washed slag and red mud in a certain proportion to obtain a carbon-based composite material. CN105131963 A discloses a soil conditioner. The soil conditioner provided by the scheme contains 45%~70% of low-temperature anaerobic carbonization of crop straw, 20%~35% of organic fertilizer, 5%~20% of humic acid, 5%~10% of clay, 5-10% of EM bacterial agent and other components according to mass fraction. It mainly solves the problem of reducing residual pesticide damage on soil contaminated by herbicides and repairing contaminated soil. CN116621169A discloses a mineral porous adsorption mineral-based biochar, which is prepared by using non-metallic tailings, crop straw, brewing dregs and calcium carbonate as raw materials; the mineral porous adsorption mineral-based biochar has the function of absorbing and retaining water, and can also adsorb nutrients such as ammonia nitrogen and total phosphorus, and has the function of adsorbing and passivating heavy metals, which can improve soil physical, biological and nutrient properties and effectively repair acidified soil. CN118307373A discloses an arsenic-cadmium-inhibiting biomass carbon-based soil conditioner, which uses a biochar-based method combined with carbonate mineralizing bacteria and sulfate-reducing bacteria to fix heavy metal arsenic and cadmium in the soil, and can effectively inhibit the movement of arsenic and cadmium in arsenic-cadmium compound-contaminated soil.

[0004] However, the above-mentioned products for soil conditioning or remediation generally have multiple problems such as single function, complex raw material sources (industrial waste, biomass materials, microbial agents, etc.), possible secondary pollution, large dosage, and general effect. In order to better save costs and effectively treat various types of polluted soils, it is urgent to develop soil conditioners with diversified functions, low costs and good effects. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a soil conditioner and a method for preparing the same and improving soil quality. The soil conditioner provided by the present invention has multiple functions such as adjusting soil pH, increasing soil organic matter content, reducing the content of heavy metal cadmium, arsenic and other pollutants in the soil, and increasing crop yields, and the dosage per mu is less than 100 kg (the average dosage in the industry is 200-300 kg / mu), without secondary pollution, and can solve the multiple problems of existing soil conditioners such as single product function, complex raw material sources, large dosage, and general effect.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a soil conditioner, which is prepared from the following raw materials in parts by weight:

[0008] Calcium chloride loaded sludge biochar: 35-45 parts;

[0009] Corn cob plant extract: 5-10 parts;

[0010] Polysilicate ferric sulfate: 5-15 parts;

[0011] Nano zinc oxide: 5-10 parts;

[0012] Phosphate minerals: 10-20 parts;

[0013] Sodium polyacrylate: 3~5 parts.

[0014] Furthermore, the calcium chloride-loaded sludge biochar is prepared by the following method:

[0015] (1) Preparation of sludge biochar: Collect sludge, preliminarily screen and remove large impurities and foreign matter therein, dehydrate to obtain dehydrated sludge blocks, crush and screen to obtain sludge particles, set the pyrolysis temperature to 300-700°C under an inert atmosphere, pyrolyze for 1-3 hours, and obtain sludge biochar;

[0016] (2) Preparation of calcium chloride-loaded sludge biochar: The sludge biochar prepared in (1) was placed in a reaction vessel, and a calcium chloride aqueous solution was added at a solid-liquid ratio of 1 g:13-15 mL. The mixture was stirred at a constant speed for 2-3 hours at room temperature, and then centrifuged and dehydrated, and then rinsed with distilled water to a pH of 7.0±0.5. Finally, the mixture was dried at a constant temperature of 80-100°C to a constant weight to obtain calcium chloride-loaded sludge biochar.

[0017] Furthermore, the collected sludge is sludge in lakes or rivers.

[0018] Preferably, the moisture content of the dewatered sludge cake is less than 60%.

[0019] Preferably, the particle size of the crushed and sieved sludge particles is less than or equal to 10 mm.

[0020] Preferably, the concentration of the calcium chloride aqueous solution is 0.4-0.6 mol / L.

[0021] Furthermore, the corncob plant extract is prepared by the following method:

[0022] The dried corn cobs are crushed into powder with a particle size of 2-3 mm, and 50%-95% ethanol is added at a ratio of 1 g:8-10 mL (mass to volume ratio), and the mixture is soaked at 70-90° C. for 3-4 hours, and filtered to obtain the corn cob plant extract.

[0023] Furthermore, the phosphate mineral is hydroxyapatite or phosphate rock powder, or a mixture of the two.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned soil conditioner, comprising the following steps:

[0025] (1) Preparation of coated nano zinc oxide: The plant extract and nano zinc oxide are uniformly mixed in a mass ratio of 1:1, and ultrasonically dispersed at room temperature for 2 to 4 hours to completely coat the plant extract on the nano zinc oxide, and then dried at a constant temperature of 80 to 100° C. to a constant weight to obtain coated nano zinc oxide;

[0026] (2) The coated nano zinc oxide prepared in (1) is then mixed evenly with the calcium chloride-loaded biochar, polysilicate ferric sulfate, phosphate mineral and sodium polyacrylate in the above weight ratio, and a proper amount of water is added. The mixture is adjusted to about 20-25° C., granulated and dried.

[0027] Preferably, in step (2), the granules are dried after granulation to a moisture content below 10%.

[0028] Preferably, the soil conditioner prepared in step (2) has a particle size of 2-3 mm.

[0029] In a third aspect, the present invention provides a method for improving soil quality, specifically, 3 to 7 days before rice transplanting, 50 to 100 kg / mu of the above soil conditioner or the soil conditioner prepared by the above preparation method is spread, and after spreading, a rotary tiller is used to perform rotary tillage to fully mix the soil and the conditioner. The spreading method is manual or mechanical.

[0030] Furthermore, the specific dosage of the soil conditioner is determined according to the soil acidity range, the degree of heavy metal cadmium and arsenic pollution, etc. Generally, 50-75 kg / mu is applied for light to moderate soil heavy metal pollution, and 75-100 kg / mu is applied for severe pollution. The degree of pollution is based on the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB15618-2018), with light pollution exceeding the standard by 1-3 times, moderate pollution by 3-5 times, and severe pollution by more than 5 times.

[0031] The mechanism of action of each component in the present invention is as follows:

[0032] 1. Biochar prepared from sludge not only contains high carbon, nitrogen, phosphorus and other elements and rich organic matter, but also has a large specific surface area and loose surface structure, has a strong adsorption capacity for heavy metal elements in the soil, and can increase soil permeability and water retention. When calcium chloride is loaded onto sludge biochar, on the one hand, the calcium ions on its surface can electrostatically attract or surface complex with cadmium and arsenic ions in the soil, thereby adsorbing them from the soil solution to the surface of biochar; on the other hand, the remaining calcium ions exchange with hydrogen ions in the soil, thereby neutralizing acidic substances in the soil and effectively reducing soil acidity.

[0033] 2. Nano zinc oxide has a large specific surface area and high adsorption capacity. It can adsorb cadmium and arsenic ions in the soil. Zinc ions and cadmium compete for adsorption and immobilize them through surface complexation, adsorption, ion exchange and other processes, reducing their bioavailability. At the same time, nano zinc oxide can increase the chlorophyll content of crops, thereby improving the photosynthesis efficiency of crops and increasing crop yields.

[0034] 3. Plant extracts such as corn cobs contain effective ingredients such as polyphenols and amino groups. On the one hand, they can coat the surface of nanoparticles to prevent nano zinc oxide from being oxidized and agglomerated by dissolved oxygen in the soil, improve its dispersibility and stability in the soil, and further enhance the adsorption of heavy metals in the soil by nano zinc oxide; on the other hand, they can also improve soil quality, increase soil organic matter content, and improve soil fertility.

[0035] 4. Polyferric silicate sulfate (PFSS) is a new type of inorganic polymer coagulant that can increase the pH value of the soil, making the soil environment more alkaline, and helping to reduce the bioavailability of cadmium and arsenic in the soil. At the same time, the iron ions in polyferric silicate sulfate can react chemically with arsenic and cadmium in the soil to form water-insoluble precipitates.

[0036] 5. Phosphate minerals can release phosphate ions to combine with hydrogen ions to form phosphoric acid that is not easily ionized, thereby neutralizing the acidity of the soil. At the same time, the phosphate ions in phosphate minerals will react chemically with heavy metal ions such as cadmium and arsenic in the soil to form insoluble phosphate precipitates. For example, cadmium ions can react with phosphate ions to form cadmium phosphate precipitates, while arsenate ions can compete with phosphate ions for adsorption sites on the soil surface and reduce the mobility of arsenic by forming more insoluble compounds.

[0037] 6. As a dispersant, sodium polyacrylate can wrap and bond the soil conditioner particles together, increasing the viscosity of the granular soil conditioner. In addition, after it is added to the soil, it can also increase the porosity of the soil, thereby improving the permeability of the soil, providing a better growth environment for plant roots and promoting plant growth.

[0038] The present invention has the following beneficial effects:

[0039] 1. The present invention can effectively protect the nano zinc oxide from being oxidized and agglomerated by coating the nano zinc oxide with plant extracts, so that the nano zinc oxide can fully play the role of soil heavy metal repair.

[0040] 2. The raw materials of the soil conditioner provided by the present invention are derived from primary minerals, plant extracts, etc., and are rich in organic matter and elements beneficial to plant growth (such as silicon, zinc, iron, etc.). They are highly compatible with the soil and have no secondary pollution. When crops are planted, they can also promote the growth of plant roots and increase crop yields.

[0041] 3. The soil conditioner of the present invention has a composite component. After processing techniques such as loading and coating, it can adjust the soil pH and reduce the effective content of heavy metal cadmium and arsenic in the soil through multi-dimensional effects such as adsorption, complexation, and precipitation, and has functional diversity characteristics.

[0042] 4. The soil conditioner of the present invention is in granular form and will not cause dust pollution when applied. After being added to the soil, it can stay in the soil for a long time to avoid being washed away by rainwater, thereby increasing the stability of the soil conditioner. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic flow chart of a method for preparing a soil conditioner provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] As used herein:

[0045] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0046] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0047] When a parameter is expressed as a range, a preferred range, or a range limited by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges of "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0048] In these examples, parts and percentages are by mass unless otherwise indicated.

[0049] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Preferred embodiments of the present invention are provided in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0051] The main raw materials and their sources used in the following examples are as follows:

[0052] 1. Calcium chloride: purchased from Tianjin Jinhui Taiya Chemical Reagent Co., Ltd., molecular formula CaCl2, AR≥96%.

[0053] 2. Polysilicate ferric sulfate: purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd., with the molecular formula of [Fe2(OH) n (SO4) 3-22 / 2(SiO2) x ] m , purity AR21.0%.

[0054] 3. Nano zinc oxide: purchased from Suzhou Yuante New Materials, purity 99.99%, specific surface area 100m 2 / g, volume density 0.3g / cm 3 , spherical, white.

[0055] 4. Hydroxyapatite: purchased from Hunan Hongcheng Ore Powder Co., Ltd., molecular formula Ca 10 (PO4)6(OH)2, specific gravity 3.16g / cm, solubility 0.4mg / L, Ca / P is 1.67.

[0056] 5. Sodium polyacrylate: purchased from Shandong Linchuan Water Technology Co., Ltd., solid content 95%, density: 1.15 g / mL.

[0057] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0058] Example 1 Preparation of sludge biochar

[0059] The present invention provides a method for preparing sludge biochar, which is as follows:

[0060] Collect sludge from lakes and conduct preliminary screening to remove large impurities and foreign matter. Dehydrate in a dehydrator to obtain dehydrated sludge blocks with a moisture content of less than 60%. Crush and screen the dehydrated sludge blocks to obtain sludge particles with a particle size of less than or equal to 10 mm. The sludge particles are placed in a pyrolysis furnace for pyrolysis to obtain sludge biomass charcoal; inert gas nitrogen is continuously introduced during the pyrolysis process to drive out the air and prevent the biomass charcoal from being oxidized. The pyrolysis temperature is set to 300~700℃ and the pyrolysis is carried out for 1~3 hours.

[0061] In this embodiment, which is a preferred embodiment, the moisture content of the dehydrated sludge block is controlled at 40%; the pyrolysis temperature is controlled at 600° C., and the pyrolysis is carried out for 3 hours.

[0062] Example 2 Preparation of Calcium Chloride Loaded Sludge Biochar

[0063] The present invention provides a method for preparing calcium chloride-loaded sludge biochar, which is specifically as follows:

[0064] Calcium chloride was dissolved in water to prepare a 0.4-0.6 mol / L calcium chloride solution. The prepared sludge biochar was placed in a reactor, and the calcium chloride solution was added at a solid-liquid ratio of 1 g:13-15 mL. The solution was stirred at a constant speed for 2-3 hours at room temperature, then centrifuged and dehydrated, and rinsed with distilled water to pH = 7.0 ± 0.5, and finally dried in a constant temperature drying oven at 80-100 ° C to constant weight to obtain calcium chloride-loaded sludge biochar.

[0065] This embodiment is a preferred embodiment. In this embodiment, a 0.5 mol / L calcium chloride solution is used, the solid-liquid ratio of sludge biochar to calcium chloride solution is 1 g:15 mL, the room temperature stirring reaction time is set to 2 hours; the constant temperature drying temperature is set to 85°C.

[0066] Example 3 Preparation of corncob plant extract

[0067] The present invention provides a method for preparing a corncob plant extract, which is specifically as follows:

[0068] The dried corn cobs are crushed into powder with a particle size of 2-3 mm using a grinder, and then 50%-95% ethanol is added at a ratio of 1 g:8-10 mL, and then soaked at 70-90° C. for 3-4 hours to obtain the corn cob plant extract.

[0069] This embodiment is a preferred embodiment. In this embodiment, 95% ethanol is selected, and the corn cob plant extract is obtained by immersing in a constant temperature water bath at 80° C. for 3 hours and filtering.

[0070] Example 4 Preparation of coated nano zinc oxide

[0071] The present invention provides a method for preparing coated nano zinc oxide, which is as follows:

[0072] The corncob plant extract prepared in Example 3 and nano zinc oxide were uniformly mixed in a mass ratio of 1:1, and ultrasonically dispersed at room temperature for 2 to 4 hours to completely coat the corncob plant extract on the nano zinc oxide, and dried in a constant temperature drying oven at 100° C. to constant weight to obtain coated nano zinc oxide.

[0073] This embodiment is a preferred embodiment. The ultrasonic dispersion time of this embodiment is set to 4 hours, and the constant temperature drying time is set to 100°C.

[0074] Example 5 Preparation of soil conditioner

[0075] The present invention also provides a method for preparing a soil conditioner, which is as follows:

[0076] (1) The components in parts by weight listed in Table 1 below are mixed uniformly, wherein the calcium chloride-loaded sludge biochar is prepared according to the above-mentioned second embodiment, and the coated nano zinc oxide is prepared according to the above-mentioned fourth embodiment. The phosphate mineral in this embodiment is hydroxyapatite as an example.

[0077] (2) After mixing evenly, add appropriate amount of water, adjust the mixture to 20-25°C, and put it into a granulator for granulation; dry the granulated mixture until the moisture content is below 10%.

[0078] This embodiment is a preferred embodiment. In this embodiment, the temperature of the mixture is adjusted to 25° C., the particle size of the soil conditioner is controlled to be 2-3 mm, and the water content of the mixture after granulation is controlled to be 5%.

[0079] Example 6 Preparation of soil conditioner

[0080] This embodiment provides a soil conditioner, the composition of which is shown in Table 1, and the preparation method is referred to Example 5.

[0081] Example 7 Preparation of soil conditioner

[0082] This embodiment provides a soil conditioner, the composition of which is shown in Table 1, and the preparation method is referred to Example 5.

[0083] The soil conditioner composed of the components of Comparative Example 1 and Comparative Example 2 in Table 1 is used as a control, and the preparation method is referred to Example 5:

[0084]

[0085] In order to verify the feasibility and effectiveness of the present invention, the soil conditioners prepared in the above embodiments and comparative examples were subjected to the following rice plot test:

[0086] A plot experiment was conducted in a rice field contaminated by cadmium and arsenic near a town. Six treatments were set up in the experiment, each with three replicates, for a total of 18 plots, arranged in random blocks. The plot size was 6m long and 4m wide, with 2.5m wide protective rows set around the experimental field, agricultural films were set up to separate the ridges, and single rows were irrigated to prevent water and fertilizer from flowing between plots.

[0087] Basic physical and chemical properties of the tested soil: soil pH is 5.65, organic matter is 29.82g / kg, total cadmium is 1.89mg / kg, total arsenic is 201.95 mg / kg, effective cadmium is 0.83 mg / kg, and effective arsenic is 26.5 mg / kg, which is moderately polluted soil. The rice variety is Xiang Zao Xian 42, purchased from Hunan Jinjian Rice Industry Co., Ltd.

[0088] Treatment 1: Blank (CK), conventional fertilization without any conditioner.

[0089] Treatment 2: conventional fertilization + soil conditioner prepared in Implementation Case 5 at 75 kg / mu.

[0090] Treatment 3: conventional fertilization + soil conditioner prepared in Implementation Case 6 at 75 kg / mu.

[0091] Treatment 4: conventional fertilization + 75 kg / mu of soil conditioner prepared in implementation case 7. Treatment 5: conventional fertilization + 75 kg / mu of soil conditioner prepared in comparative case 1.

[0092] Treatment 6: conventional fertilization + soil conditioner prepared in comparative case 2 at 75 kg / mu as base application.

[0093] On the basis of conventional fertilization, the conditioner is evenly spread on the field surface by manual or mechanical spreading 7 to 10 days before plowing, and the field is plowed twice with a rotary tiller to mix it evenly with the soil. The appropriate amount of water is poured to stabilize and mature for 3 to 5 days before rice transplanting. During the rice growth period, weeding, fertilization, pesticide spraying and irrigation are carried out according to local production management methods.

[0094] When the rice is mature, collect 1-1.5 kg of soil samples, air-dry them naturally, grind them and pass them through a 20-mesh sieve (for pH value) and a 100-mesh sieve (for analyzing the total cadmium and total arsenic content in the soil), mix them evenly, and put them into sealed bags according to their numbers for storage.

[0095] 1-1.5 kg of rice samples were collected, and the rice grains were husked by a huller to obtain rice grains. The rice grains were dried and ground, passed through an 80-mesh sieve to remove impurities and particles, and stored in sealed bags for later use.

[0096] Soil pH value, available cadmium, and available arsenic were measured, and rice yield, rice cadmium, and rice arsenic content were measured in rice. The test methods are as follows:

[0097] Soil pH determination method: Use water as the extractant, collect a small amount of soil and mix the water and soil in a mass ratio of 2.5:1, and measure it using the potentiometric method (refer to NY / T1377-2007).

[0098] Determination of available cadmium in soil: refer to “Determination of Available Lead and Cadmium in Soil Quality by Atomic Absorption Method” (GB / T23739-2009).

[0099] Determination of available arsenic in soil: refer to "Determination of Available Arsenic and Available Mercury in Acidic Soil by Atomic Fluorescence Method" (DB35 / T 1459-2014).

[0100] Rice yield determination: refer to "Rice Yield Determination Operation Specification" (DB33 / T 2517-2022).

[0101] Method for determination of cadmium in rice: refer to "National Food Safety Standard Determination of Cadmium in Food" (GB 5009.15-2023).

[0102] Method for determination of arsenic in rice: refer to "National Food Safety Standard Determination of Total Arsenic and Inorganic Arsenic in Food" (GB5009.11-2024).

[0103] 1. Effects of different treatments on soil physical and chemical properties

[0104] After testing, the test results of the effects of different treatment groups on soil physical and chemical properties are shown in Table 2:

[0105]

[0106] As can be seen from Table 2, the soil pH value of treatment 1 (CK) was 5.65 and the soil organic matter content was 29.82 g / kg. Compared with treatment 1, treatments 2, 3, 4, 5 and 6 all increased the soil pH value and soil organic matter content to a certain extent.

[0107] Among them, the soil pH improvement rates were 7.61%, 8.49%, 9.91%, 2.83% and 5.84% respectively, and the improvement effect was treatment 4>treatment 3>treatment 2>treatment 6>treatment 5.

[0108] The soil organic matter improvement rates were 4.12%, 4.19%, 4.43%, 3.82% and 2.78% respectively, and the improvement effect was treatment 4 > treatment 3 > treatment 2 > treatment 5 > treatment 6.

[0109] 2. Effects of different treatments on soil available cadmium and available arsenic content

[0110] After testing, the results of the different treatment groups on the effective cadmium and effective arsenic content in the soil are shown in Table 3:

[0111]

[0112] As can be seen from Table 3, the effective cadmium content in the soil of treatment 1 (CK) was 0.83 mg / kg, and the effective arsenic content in the soil was 26.5 mg / kg. Compared with treatment 1, treatments 2, 3, 4, 5, and 6 all reduced the effective cadmium and arsenic contents in the soil to a certain extent.

[0113] Among them, the reduction rates of soil available cadmium were 48.2%, 50.6%, 57.8%, 30.1% and 26.5% respectively, and the reduction effect of treatment 4>treatment 3>treatment 2>treatment 5>treatment 6.

[0114] The reduction rates of effective arsenic content were 52.5%, 55.5%, 62.6%, 27.5% and 36.9% respectively, and the reduction effect was treatment 4>treatment 3>treatment 2>treatment 6>treatment 5.

[0115] 3. Effects of different treatments on rice yield

[0116] After testing, the results of the experiment on the effect of different treatment groups on rice yield are shown in Table 4:

[0117]

[0118] As can be seen from Table 4, the rice yield of Treatment 1 (CK) was 489.6 kg / mu. Compared with Treatment 1, Treatments 2, 3, 4, 5, and 6 all increased rice yield to a certain extent, with increases of 7.07%, 8.15%, 9.42%, 4.41%, and 3.82%, respectively. The improvement effect was Treatment 4 > Treatment 3 > Treatment 2 > Treatment 5 > Treatment 6.

[0119] 4. Effects of different treatments on cadmium and arsenic content in rice

[0120] After testing, the results of the effects of different treatment groups on the cadmium and arsenic content of rice are shown in Table 5:

[0121]

[0122] As can be seen from Table 5, the cadmium content of rice in treatment 1 (CK) was 0.62 mg / kg, and the arsenic content of rice was 1.36 mg / kg. Compared with treatment 1, treatments 2, 3, 4, 5, and 6 all reduced the cadmium and arsenic contents of rice to a certain extent. The reduction rates of cadmium in rice were 61.3%, 64.5%, 70.9%, 30.6%, and 25.8%, respectively, and the reduction effect was treatment 4>treatment 3>treatment 2>treatment 5>treatment 6. The reduction rates of arsenic in rice were 73.5%, 77.2%, 85.3%, 24.3%, and 44.9%, respectively, and the reduction effect was treatment 4>treatment 3>treatment 2>treatment 6>treatment 5.

[0123] Treatment 4 had the best effect, and the cadmium and arsenic content of rice both reached the "National Food Safety Standard Limits of Contaminants in Food" (GB 2762-2022).

[0124] In summary, the soil conditioner provided by the present invention can adjust the pH of the soil, reduce the effective content of heavy metal cadmium and arsenic in the soil, promote the growth of plant roots, increase crop yields, and has functional diversity characteristics.

[0125] The above descriptions are only some preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A soil conditioner, characterized in that: Made from the following raw materials in parts by weight: Calcium chloride loaded sludge biochar: 35-45 parts; Corn cob plant extract: 5-10 parts; Polysilicate ferric sulfate: 5-15 parts; Nano zinc oxide: 5-10 parts; Phosphate minerals: 10-20 parts; Sodium polyacrylate: 3-5 parts; The calcium chloride-loaded sludge biomass charcoal is prepared by the following method: S1. Preparation of sludge biomass charcoal: collecting sludge, preliminarily screening to remove large impurities and foreign matter therein, dehydrating to obtain dehydrated sludge blocks, crushing and screening to obtain sludge particles, setting the pyrolysis temperature to 300-700°C under an inert atmosphere, pyrolyzing for 1-3 hours, and obtaining sludge biomass charcoal; S2. Preparation of calcium chloride-loaded sludge biochar: placing the sludge biochar prepared in S1 in a reaction vessel, adding a calcium chloride aqueous solution at a solid-liquid ratio of 1 g:13-15 mL, stirring at a constant speed for 2-3 hours at room temperature, centrifugally dehydrating, and then washing with distilled water to pH = 7.0 ± 0.5, and finally drying at a constant temperature of 80-100 ° C to constant weight to obtain calcium chloride-loaded sludge biochar; The corncob plant extract is prepared by the following method: The dried corn cobs are crushed into powder with a particle size of 2-3 mm, 50%-95% ethanol is added at a ratio of 1 g: 8-10 mL, and the mixture is soaked at 70-90° C. for 3-4 hours, and filtered to obtain the corn cob plant extract; During the preparation, the corn cob plant extract and the nano zinc oxide are firstly mixed uniformly in a mass ratio of 1:1, ultrasonically dispersed at room temperature for 2-4 hours to completely coat the corn cob plant extract on the nano zinc oxide, and then dried at a constant temperature of 80-100° C. to a constant weight to obtain coated nano zinc oxide; and then mixed with other components in weight to form granules to obtain the soil conditioner.

2. The soil conditioner according to claim 1, characterized in that The collected sludge is from lakes or rivers; the moisture content of the dewatered sludge blocks is less than 60%; the particle size of the crushed and screened sludge particles is less than or equal to 10mm.

3. The soil conditioner according to claim 1, characterized in that The concentration of calcium chloride aqueous solution is 0.4~0.6mol / L.

4. The soil conditioner according to any one of claims 1 to 3, characterized in that The phosphate mineral is hydroxyapatite or phosphate rock powder, or a mixture of the two.

5. A method for preparing the soil conditioner according to any one of claims 1 to 4, characterized in that: The details are as follows: First, the corn cob plant extract in the raw material and nano zinc oxide are used to prepare coated nano zinc oxide; then the prepared coated nano zinc oxide is evenly mixed with biomass charcoal loaded with calcium chloride, polyferric silicate sulfate, phosphate mineral and sodium polyacrylate in the weight proportion in the raw material, a proper amount of water is added, the mixture is adjusted to 20-25° C., granulated and then dried to a moisture content of less than 10%.

6. The preparation method according to claim 5, characterized in that: The particle size of the prepared soil conditioner is 2-3 mm.

7. A method for improving soil quality, characterized in that: The soil conditioner according to any one of claims 1 to 4 or the soil conditioner prepared by the preparation method according to any one of claims 5 to 6 is spread at 50 to 100 kg / mu 3 to 7 days before rice transplanting, and then rotary tilled with a rotary tiller to fully mix the soil and the conditioner.

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